Telephone-exchange system.



J. D. BONNAR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. \1. 1912. RENEWED FEB. 20. m7.

y Patented July 17, 1917.

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J D. BONNAR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 11. 1912. RENEWED FEB. 20. um.

lfiwfiww Patented Jul n, 191?.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 11011.11. 1912. RENEWED FEB- 20.1911.

K Patented Ju1y17,1917.

l0 SHEETS-SHEET 3.

J. D. BONNAR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 11, I912- RENEWED FEB. 20 1917. 1 38,837 Patented July 1, 1917.

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TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED NOV.H.19|2- RENEWED FEB,20.19I7. 8 Patented July 17, 1917.

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amt [91400000 TEAM/m J. D. BONNAR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV 11. m2. RENEWED FEB. 20. 1911 Patented July 17, 1917.

J. D. BONNAR.

TELEPHONE EXCHANGESYSTEM.

APPLICATION FILED NOV. H. 1912. RENEWED FEB. 20.19l1.

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TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED NOV. 11, l9i2- RENEWED FEB. 20. 1917.

1 9 33 3' Patented July 17, 1917.

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TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED NOV. 11. I912 RENEWED FEB. 20.

19 I 7- 1,33,3'? Patented July 17, 1917.

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J. D. BONNAR.

TELEPHONE EXCHANGE SYSTEM.

RENEWED FEB. 20-19IY.

Patented July 17, 1917.

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JAMES n. routine, or Asnrannna, onto, assumes, BY ransnn essrenlvrni'r'rs, 're

JAMES R. GARFIELD, 'rnus'rnn, or CLEVELAND, OHIO.

TELEPHONE-EXCHANGE SYSTEM.

Application filed November 11, 1912, Serial No. 730,7M. Renewed February 20 1917. Serial No. 149,953.

To all whom it may concern:

Be it known that I, JAMns D. BoNNAR, a citizen of the United States of America, residing at Ashtabula, in the county of'Ashtabula and State of Ohio, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a specification.

My invention relates to telephone exchange systems and especially to that class wherein automatic switching mechanism is employed in establishing connections between subscribers.

The general object of this invention is the improvement of the systems mentioned.

Some of the improvements may be stated as foll0ws: I

To control the manner in which the pri mary switches pick out or select, the calling line. The primary switches being controlled in such a manner that the calling lines are selected without preference:

To distribute the trunks so that the calling lines will be connected to a key-board in'g device, or devices, to the switching mechanism.

The calling lines are connected to primary trunks by means of primary switches. The primary trunks are selectedby secondary switches and the key-boards selected by what I term tertiary switches. Each secondary switch has an associated tertiary switch, which start to perform their selecting functions at the same time.

My invention is illustrated in the acc0m panying drawings wherein:

Figure 1 shows a subscribers lineequipment and a control circuit for the primary switches.

Fig. 2 shows a primary and firstselector switch.

Fig. shows a second selector switch.

Fig. 4 shows a connector switch with its associated party line selecting switch.

Fi 5 shows the circuit of a called line, together with a primary control circuit and is a duplicate of that shown in Fig. 1.

Fig. 6 shows a secondary control circuit for starting, or regulating a secondary switch.

Fig. 7 shows a secondary switch and its associated tertiary switch.

Fig. 8 shows the circuits and shifting switch interposed between the tertiary switch,

and the key-board.

Fig. 9 shows the operators key-board and sending device.

Fig. 10 shows the arrangement of the various figures for tracing a call.

Referring to Fig. 1, the subscribers sta tion at A is equipped with apparatususual 1n common battery exchanges, and the line wires from this station terminate at the central oliice in a line relay 2. The line'relays are divided into groups, there being ten groups to each one hundred lines. Each group of ten line relays has an associated group relay 3. The object of this group relay is to cause the switch J to start in search of the actuated group relay, which designates the group of ten in which the calling line is located. The bank of contacts J controls the testing of the switch J for locating the actuated group relay. The bank contacts of J are connected directl y to corresponding row contacts in primary selector switches. As soon as the switch J comes to rest upon finding the group in which the calling line is located, then ground is connected by the medium of the switch J to the row contact of the primary switch.

If any group relay when energized connected ground directly to the row, contact of the primary switch, then the primary switch in rotating would naturally cngage the first contact active and thereupon pick out the line associated with this group contact. By interposing the switch J, ground is only connected to a single contact in the primary switch and that without any preference, for it is just as liable for the ninth contact in the primary switch to become grounded as it is for the first contact to become grounded.

lif this provision were not made, then it Patented July it, 191?.

would naturally follow during rush hours that the lines numerically lower would be the first selected.

The switch W starts to rotate as-soon as the switch J comes to rest upon finding the group in which the calling line is located. The switch W will continue to rotate until an idle primary switch is found, whereupon the test relay 5 becomes energized, thereby preventing any further action of the switch W.

Relay 2 connects ground directly to the individual test contacts in the banks of'the primary switch. The primary switch first rotates to pick out the group in which the calling line is located, and then steps ver' tically until the individual test contact is reached. As soon as this contact is engaged by the wipers of the primary switch C, relay 1 is energized, thereby disconnecting relays2 and 3.

Referring to Fig. 2, the primary switch C is shown for picking out the calling line. This switch ,first rotates until the rotary test wiper 64' picks out the active row contact and after reaching, this contact, the switch ceases to rotate and steps .vertically until the individual test contact leading to the line relay 2 is found. The first selector switch is shown at D and responds to impulses from the sending device to pick out an idle trunk leading to the second selector switch in the proper row.

The wipers '63 of the primary switch C and wipers 56 of the first selector switch D are joined as indicated by the heavy lines for conversational purposes. The tip and sleeve conductors are separated by the condensers 43 and 44. Relay 23 and the retardation coil 26 are connected respectively to. the free and grounded side of battery and thus furnish talking current to the calling subscriber. 21 is t e starting relay of the primary switchand corresponds some what to the line relay2 (Fig.1) ,as it contiols the, action of the secon ary switch (Fig. 7). 22 is the rotary. testrelay, while 24 is the individual test relay. Relay 25 is operated when the secondary switch picks out the calling trunk. This relay remains energized while impulses are being transmitted to prevent the calling subscriber hear-.

ing clicks. 27 is a test relay of the first selector switch D and is actuated by the test impulse from the sending device and re- 'ma1ns energized while the first selector switch is seeking. an idle second selector; Relay 28'is energized whenever either the rotary or vertical magnets of the primary switch are operated, and also when the vertical magnet of the first selector switch is operated. The circuits of these magnets are normally completed through the backcon tacts of relay 28 and so, therefore, whenit is actuated the magnet circuits are opened. The vibrating action set up between the relay and the magnets causes the latter to step the switches with which they are associated. Tihe' resistance coil 42 is placed in series with the winding of the rotary relay 29. This relay receives impulses from the sending de vice and operates lmtgl'lct 34, causing the switch D to rotate. lVhen magnet 34 operates, it closes its associated contact springs andplaces ground between the resistance coil 42 and the winding of relay 29. As soon as this ground is connected in this manner, relay 29 is shunted. It therefore follows that the impulses from the sending device are regulated insomuch that after the mag net completes its stroke, the relay which 0perated it is at once disabled. This arrangement does away with the necessity of fine adjustment between the repeating relay, the

magnet and the sending device.

In case the impulse conductors over which the impulses are transmitted accumulate static charge, then this charge is dissipated by the ground being connected after each impulse.

Referring now to Fig. 3, the second selector switch I) is operated, first in a rotary direction to pick out the row, and then in a vertical direction to pick out an idle contact in the row and is similar to the first selector switch shown at D. 81 is the repeating relay and is in series with regulating coil 86. 82 is the interrupter relay for causing the stopping of the switch E in a vertical direction, after the test impulse has been transmitted. 83 is the test relay associated with the second selector and remains energized while the wipers of the switch E are passing over busy contacts leading to connector switches. Relay 80 is energized at the first action of relay 81 and controls the release circuit of the second selector switch and also maintains this switch busy against other calls, until it reaches its normal position.

Referring to Fig. 4 the connector switch G is provided with a set of wipers 390, which engage contacts leading to the tip and sleeve conductors of the called line, and also with wipers 391 which engage contacts connected to the cut-off relay of the called line. These latter wipers also serve as test wipers over which the condition of the called line is controlled. 305 and 310 are repeating relays and respond to the impulses from the sending device. 315 is a control relay and when operated removes relay 325 and the retardation coil 335 from the wipers, while the connector switch G is passing over busy contacts. 320 is the tipbattery supply relay and responds when the called subscriber removes his receiver. 340 is the ringing relay operated by a suitable commutator 370. This relay is rendered active when the conmasses nector switch wipers engage contacts leading to the called line. This relay is disabled when the tip relay 320 is energized upon the called subscriber removing his receiver. The actuation of relay 320 unlocks the control relay 330. 345 is'the busy test relay and is actuated when a busy line is found. This relay, under these conditions, locks itself to ground through the test wire 306. The action ofthis relay connects a suitable busy tone test to the calling subscriber, notifying him that the line called for is busy. The action of the test relay closes the circuit of release magnet 365, thereby restoring the switch Gr.

A party line selecting switch is shown at F. The contacts and wiper of the portion JJ connect the generators 356, 357, 358 or 359 to either the tip or sleeve contact of the ringing relay 340. The contacts and wiper of the portion I serve to restore the switch to its normal or idle position. The contacts and wiper of the portion H serve to connect ground to either the tip or sleeve contacts of the ringing relay 340. When the portion JJ cuts on generator to the tip contact, then the portion H connects ground to the sleeve contact, and when the portion JJ connects generator to sleeve contact, the portion H connects ground to the tip contact. With this arrangement it is possible to ring subscribers bells which are connected to either the tip or sleeve side of the line to ground as well as to ring them when they are bridged directly across the tip and sleeve conductors. Portion H of the switch also serves to release connector switch G after the called subscriber hangs up his receiver, or when the calling subscriber hangs up his receiver, in case the called subscriber does not answer.

When the switch F is in its normal position, the wiper of the portion H rests on the contact 334, the wiper of I on the contact of 336, while the wiper of J J rests upon the contact 338.

Whenever the ringing relay 340 is actuated, it connects a suitable ring-back signal to the calling subscriber, notifying him that the party he called for is being rung.

The two repeating relays 305 and 310, each have their windings common tothe resistance coil 470. In the connector circuit, the impulses are regulated by both the rotary and vertical magnets 350, and 355, respectively, and also by the action of magnet 360 controlling the switch F.

Referring to Fig. 6, the switch shown at Y corresponds to the switch W (Fig. 1) and serves to pick out an idle secondary switch.

The switch X is a time element control and only comes into action when the relays 130 and 132 have been held energized for an abnormal length of time. The relay 132 is energized as soon as an idle secondary switch is picked out, and should only remain energized long enough for a secondary switch Fig. 7) to rotate to the tenth row and step vertically to the tenth contact in the tenth row. The magnet 77 causes the switch X to rotate when the contact springs 36 are closed by a suitably timed circuit closer. This set of contacts 36 can be located on the sending device and closed once at each rotation.

' We will assume that the relays 132 and 130 have been held energized beyond the maximum time and the switch X is rotating. When the wiper m reaches one of the contacts connected to the wire 139, the circuit of relay 78 is closed to ground through the contacts of relay 132. tinues to step at each rotation of the sending device, and when the wiper 00 reaches one of the contacts to which the relay 76 is connected, this relay operates and performs the following functions: Ground is placed on the wire 149 through the wiper and contacts of the lower bank of the switch W (Fig. 1.) to wire 60 operating relay 29,thereby causing the switch D to take one step. Ground is also placed on wire 144, 142, to the release magnet 166 of the switch M, thereby restoring it. The wires 18 and 148 are also opened, thereby disconnecting relay 5 and relay 21. The falling back of this latter relay, disconnects relays 130 and 132 (Fig. 6) thereby unlocking relay 78, and no further action takes place.

If a calling subscriber is connected to the primary switch (I and a faulty connection takes place, as just described, he can hang up his receiver and as the switch Dhastaken one step, the circuit of the release magnet 32 is closed and the switch 0 will restore, after which the switch D drops back. After hanging up, the subscriber can make a recall and become connected to another trunk.

The switch X performs no functions with regular connections, unless the key-set switch and trunk should become tied up, where upon it comes into play and releases the tied-up apparatus.

Referring to Fig. 7 the secondary switch M for picking out the calling primary trunk and the tertiary switch MM for picking out an idle key-board, are shown. The switch M is similar to the primary switch C and first rotates in order to pick out the group in which the calling trunk is located and then steps vertically to pick out the trunk in the group. 168 is the row test wiper while wipers 167 engage contacts leading to the primary trunk over which the impulses are transmitted. The wipers 169 are used for testing for the individual contact and for exercising control over the primary trunk.

The switch MM is of a rotary type and provided with four sets of bank contacts and wipers. In the drawing this switch is shown The switch X conin its normal or resting position. When in this position, the mm springs K are as shown.

Relay 152 is the starting relay and is ener gized when the switch Y picks out the idle switch M. The action of relay 152 causes the switch M to start in search of the calling primary trunk and at the same time causes the switch MM to Search for an idle keyboard. 153 is the row test relay, while 154 is the individual test relay. 179 is operated when the primary trunk is picked out and connects the relay 180 to the tip conductor, the combination, which will be explained later, controls the release of the switches M and MM. 264: is operated by relay 152 and places relays 263 and 162 in series. These two latter relays are the test relays for the tertiary switch MM. The test wires of the switch MM are'associated with the portion I. The control wires extending to Fig. 8 are connected to contacts in the portion H. The tip and sleeve conductors are connected respectively to contacts in the portions F and G.

Each secondary switch M has an associated tertiary switch MM. The contacts in the banks of each of these switches are multipled to the bank contacts of other M and MM switches, with exception of the row contacts engaged by the row wiper 168 in the switch M. This row contact is individual andv connected to contacts in the switch Y and is rendered active when the switch Y picks out an idle switch M.

Referring to Fig. 8, 156 is the signal relay and energized when the switch MM picks out the key-board. The action of this relay causes the signal lamps 243 and 241 to light. Relay 192 is operated by relay 156 so as to place the answering relay 155 under control of the operator, as ordinarily she cannot affect this relay. When the an swering relay is operated, it connects the operators telephone set directly to the tip and sleeve conductors allowing her to converse with the calling subscriber. The operation of relay 155 unlocks relay 156. 157 is the starting rclay'operated when the starting button 247 is pressed. The action of this relay connects the starting cam on the sending device, (Fig. 9) to the stepping magnet 161 of the shifting switch, shown in Fig. 8. This stepping magnet is operated once at each rotation of the sending device and operating the shifting switch cuts on the impulses from the key-board in a predetermined order. The order of these impulses is as follows: At the first rotation of the sending device, impulses corresponding to the thousands are sent over the tip side of the trunk and at the second rotation a single test impulse is sent over the sleeve side of the trunk. At the third rotation the hundred impulses are sent over the tip side of the trunk and at the fourth rotation a single test impulse is sent over the sleeve side. At the fifth rotation, impulses for operating the selective switch associat i with the connector are sent over the tip side of the trunk and at the sixth rotation the tens impulses are sent over the sleeve side of the trunk. At the seventh rotation the units impulses are sent over the tip side of the trunk and at the eighth rotation a single test impulse is sent over the sleeve side of the trunk.

At the next rotation of the sending device, the wiper of the portion P passing over its contacts, closes the circuit of the release relay 158 causing the shifting switch to rapidly rotate until it reaches its normal position. The operation of this relay also severs the control conductor leading to contacts in the switch MM and serves to cause the release of the switch M. 185 is the interrupter relay for causing the automatic stepping of the magnet 161.

Referring to Fig. 9 the operators keyboard and sending device are shown. The key-board consists of five rows of buttons, each row having ten buttons. No. 1 button of each row is connected to a contact operated by the cam 232 on the sending device. No. 2 button of each row is connected to a contact operated by the cam 233. Corresponding buttons in each row are connected to the same contact. The contact controlled by the cam 232 is closed just long enough to keep the relay 160 (Fig. 8) energized while one impulse is being transmittcd by the commutator 242. If No. 10 button is pressed, the relay 160 will be closed by the cam 241 long enough for ten impulses to be transmitted by the commutator 242. The contacts of the commutator 242 are connected directly to a normally open contact of relay 160 and when this relay is energized the impulses are connected to either the tip or sleeve side of the trunk, depending upon the position of the arm of the shifting switch in regard to the contacts of the bank N.

The buttons or keys shown in the rows R. S. T. U. and V are of the usual locking and indicating type. When any one button in a certain row is pressed, it will release the button formerly pressed. The buttons 246, 247 and 248 are of the non-locking type and the contacts controlled by them are only closed while the operator presses the button.

I have described and illustrated but a single set of link circuits from the calling to the called subscriber, and only one setof operators secondary and tertiary switches. In ordinary practice there would be ten per cent, or ten primary trunks, such as shown t eater in Fig. 2, for serving one hundred lines. Each one hundred lines would be provided with a set of control switches W and J, such as shown in Fig. l.

The ten primary trunks would be provided with a switch Y for picking out secondary trunks. By providing an individual switch Y for each set or group of primary trunks, I am enabled to bring in simultaneous calls from different groups of one hundred lines.

Each operator is provided preferably with three key-boards such as shown in Fig. 9, for enabling her to handle calls without loss of time, for while one call is being built up on one key-set another call can become connected to another key-set.

The cams of the sending device, shown at 230, to 241 inclusive may be common to a group of key-sets. The commutator 242, however, is preferably individual to one key-board, or to one operator.

Each trunk as shown in Fig. 7 has an associated secondary and tertiary switch, and the tertiary switch can be provided with a large number of contacts so that even in a large exchange any key-board may be selected.

The grouping of the various trunks and the number of key-hoards will depend entirely upon trailic conditions.

' In the present instance I have shown the exchange to be of ten thousand lines capacity, and in case of larger exchanges, it would be only necessary to add additional selector switches and additional rows of buttons to the operators keyboard for controlling the same.

The operation of the system in detail as outlined in the foregoing description is as follows:

We will assume that the subscriber at A desires to converse with a subscriber at AA, and the various circuits or figures arranged in accordance with Fig. 10.

Subscriber A removing his receiver closes the circuit of the line relay 2. The operation of this relay closes the circuit of the group relay 3, which in turn closes the circuit of relay 4. The operation of relay 3 connects ground to a contact in the back J of the switch J. The operation of relay 4 completes the circuit of the stepping magnet 12 0f the switch J, thereby causing this switch to rotate until the wiper of the portion J reaches contact rendered active by the operation of relay 3. As soon as this contact is found, the circuit of relay 6 is closed, which opens the circuit of the magnet .12 and me vents further operation of the switch J. The operation of relay (3, also closes the circuit of the stepping n'iagnct 7 of the switch l/V through the contacts of relay 5. This switch will continue to rotate until the wiper of the portion a engages a contact leading to an idle primary switch, such as shown on Fig. 2. As soon as such an idle trunk is found, relay is placed in series with relay 21, (Fig. 2) as follows: ground, contact of relay 6, 5, 18, contacts of relay 76, (Fig. 6) 148, w, 14, 21, 70, contact of relay 24 to battery B. Relay 5 becoming energized, opens the circuitof the stepping magnet 7 causing the switch \V to cease rotating. Relay 21 operating closes the circuit of the retary stepping magnet 31 of the swtich C, as follows: battery B, 80, back contact of relay 24, 71, contact of relay 28, back contact.

of relay 22, 31 to ground. The operation of magnet 31 causes the primary switch C to rotate until the wiper 64 reaches the grounded row contact. This ground is connected to the row contact as follows: ground, contacts of relay 6, J, 13, to row contact.

This row wiper ()4 is mounted on thesame spindle with the wipers (33 and 65, and while the switch is rotating, the wiper 64 engages the contact rendered busy by the action of relay (3 and the switch J. As there are one hundred lines to a group, and ten sets of group relays, it therefore follows that there are ten row contacts which the wiper 64 engages. There are ten sets of individual contacts arranged in. vertical rows, associated with each row contact, and which the wipers G3 and 65 respectively engage. It therefore follows that after the switch picks out the group in which the calling line is located. it will. afterward step vertically until the wipers engage contacts associated with the calling line.

As soon as the row contact is found the circuit of relay 22 is closed as follows: battery B, 80, contacts of relay 24, 71, 22, G4, 18, J, to ground, through the contacts of relay 6. Relay 22 operating, disconnects the rotary magnet 31 and in its place connects vertical magnet 30, thereby causing the switch 0 to step vertically until the individual test contact associated with the calling line is found. As soon as this contact is reached, the circuit of relay 24 is closed as follows: battery B, 24, (38, front contact of relay 22, 67, 11, contacts of relay 2 to ground, through the contacts of relay 1. Relay 24, operating, opens the wire 71, dis. connecting relay 22, which in. falling back, disconnects relay 24 from wire 67 and con nects it instead to wire on. Relay 24 is now placed in series with relay 1, and the operating of this latter relay disconnects line relay 2, and consequently relay 3. Relay 3 falling back, disconnects relay 4. Relay 3 also removes ground from the portion J of the switch J, thereby releasing relay 6. Relay (5 falling back removes ground from the row test contact of the switch C.

The operating of relay 24 connects battery to the winding of relay 23, and the falling back of relay 22 connects ground to the retardation coil 26 and battery is thereby supplied to the calling: subscribe; for talking purposes.

Relay 21 remains energized until the primary switch G finds the calling line and. until the secondary switch M finds the calling trunk. The action of relay 21 connects battery to relay 130 over wire 79, thereby operating it so as to cause the action of the switch Y. The action of relay 21 also connects battery to the individual test con tacts of the secondary switch M (Fig. 7).

The action of relay 130 closes the circuit of the stepping magnet 133 through the normally closed contacts of relays 132 and 131. The magnet 133 in operating, closes the circuit of the interrupter relay 134, which in turn opens the circuit of the magnet itself, thereby causing the switch Y to step. The switch Y will continue to step until an idle secondary switch is found, such as shown in Fig. 7. \Vhen this switch is found relay 131 is placed in series with relay 152, as follows: ground, contacts of relay 130, 131, 138, upper bank contacts of Y, 140, contacts of relay 266, 152, cam springs 196 to battery B.

Relay 131 operating, connects battery on wire 136 to relay 132, causing the latter to operate. The operation of this relay places ground on wire 138, thereby shunting relay 131. This direct ground is connected through the switch Y to the test wire 140 which is multipled to other Y switches, thereby rendering the selected secondary switch M busy against other calls. The operation of relay 132 also connects ground to the row contact of the switch M, as follows: ground, 139, middle portion of switch Y, 141, to the row contact in switch M. lielay 152 in operating, completes the circuit.

of the rotary magnet 165, through the contacts of the interrupter relay 163, thereby causing the switch M to rotate. The opera tion of relay 152 also closes the circuit of relay 264:, which has its circuit maintained While relay 152 is energized and also while relay 162 is energized. After the switch M starts to rotate, the cam springs 196 are opened, but the circuit of relay 152 is maintained through the back contacts of relay 154:.

The operation of relay 264 places relays 263 and 162 in series as follows: ground, normally closed cam springs K, 213, contacts of relay 264, 263, 162 to battery B. The operation of relay 263 conn'iletes the circuit of the stepping magnet 261 of the switch MM as follows: ground, back contacts of relay 285, contacts of relay 263, 261 to battery B. The operation of magnet 261. closes the circuit of the interrupter relay 285, thereby causing magnet 261 itself to vibrate and causes switch MM to rotate. The oporation of relay 162 scvers the tip and sleeve conductors to prevent interference while the switch MM is rotating. The action of this elay also connects ground to the locking contact of relay 261, thereby maintaining its circuit closed in case relay 152 should fall l. ack. It may be that the switch M will find the calling trunk located in the first row and first contact and provision has to be made to keep the circuit of relay 26-1 closed after relay 152 falls back, and before the switch MM picks out an idle key-board.

At the first step of the switch MM, the normally closed cam contacts K are broken and the set normally opened are closed. After the normally open contacts are broken the circuit of relays 263 and 162 are maintained by the wiper of the portion I of the switch MM engaging busy, or grounded contacts. This new maintaining circuit can be traced as follows: ground, contact of the portion '1 contacts of relay 263, back contact-s of relay 266, 263, 162 to battery B. From the circuit just traced, it will be noted that the energizing of relays 263 and 162 depend upon the wiper of the portion I engaging busy, or grounded contacts. As soon as an idle contact is found, that is free from ground, then relays 263 and 162 become deenergized, thereby causing the switch MM to come to rest with its wipers engaging contact-s leading to an idle key-board. Relay 162 falling back closes the tip and sleeve trunk conductors and opens the circuit of relay 264. Assuming that the switch M has found the calling primary trunk then relay 152 would be decnergized and relay 261- would fall back.

1 have described how the switch MM picks out the idle heyboarr'l and will now return to the operation of the switch M. The relay 152, as already stated, is energized when the switch M is picked out by the switch Y, thereby causing the rotation of the switch M until the wiper 168 finds the active row contact, \VllOJfGlll'NJIl relay 153 becomes energized, disconnects rotary magnet 165, and in its place connects the vertical magnet 164. As soon as this magnet is cormectcd the switch will step vertically until the individual test contact leading to the calling trunk is reached, whereupon the circuit of relay 154 is closed as follows: ground, 154., 172, 169, 62, 80, contacts of relay 21 to battery B. The operation of relay 154 disconnects relay 152, thereby preventing further action on the part of the switch M. The operation of relay 154 also closes the circuit of relay 17$). The operation of this latter relay connects the winding of relay 180 to the tip conductor 150. The falling back of relay 152 besides preventing further action of the switch, also unlocks relay 153.

assess? This latter relay falling back places relays 25, 265, 156 in series by the following path: starting from Fig. 8, ground, back contacts of relay 157, 202, ack contacts of relay 155, 217, 156, back ontacts of relay 151, 275, H, 175, back contacts of relay 263, 214 265, back contacts of relay 153, 170, 169, 59, 25 to battery B, through the contacts of relay 24. The operating of relay 25 releases relay 21, (Fig. 2) and also relay 5 (Fig. 1). The release of relay 5 frees the switch W so as to place it in condition to pick out other primary switches.

The operation of relay 25 in disconnecting relay 21 causes battery to be removed from the individual test contact in the switch M. Battery being removed in this manner, al lows relay 154 to fall back. The operation of relay 265, (Fig. 7) and the operation of relay 179 at the same time, serve to hold open the circuit of relay 266. When the latter relay is operated, the release magnet 166 of the switch M is closed and also the stepping magnet 261 of the switch MM.

The operation of relay 156, (Fig. 8) closes the circuit of relay 192. The locking circuit of this latter relay has its circuit controlled through the contacts of relay 158. The action of relay 156 closes the circuit of K the lamp 243, as follows: battery B, contacts of relay 156, 181, 243 to ground. The action of this relay also closes the circuit of lamp 244 as follows: battery B, contacts of relay 156, 183, 244, to ground.

The lighting of these two lamps notifies the operator of a call.

Referring again to Fig. 2, it will be noted that as soon as relay 21 is disconnected that the circuit of relay 130, (Fig. 6) is broken, and this relay in falling back in turn opens the circuit of relay 132, thereby. placing the switch Y in condition to pick out other secondary switches.

The operator perceiving the lighting of the two lamps, presses the answering button 248, thereby closing the circuit of relay 155, as follows: ground, 248, 182, 155, contacts of relay 192, to battery B. The operation of relay 155 connects the operators telephone set, indicated at 197 across the tip and sleeve conductors 250 and 251 respectively. The operation of relay 155 opens the circuit of relay 156, thereby extinguishing the lamps 243, and 244, but causing lamp 245 to light instead. The disconnecting of relay 156 by 155, allows relays 265 and 25, with which it is in series. to also fall back. Relay 25 falling back closes the tip and sleeve conductors of the primary trunk, thereby allowing the operator to converse with the calling subscriber. Upon receiving the number desired, she presses the proper buttons in the rows R. S. T. U. and V. The depressed buttons will correspond to the number of, the called subscriber. After setting up the proper number on her keyboard, the operator presses button 247, thereby placing relay 157 in series with relays 265, and 25 as follows: ground, 247, E86, 218, 157, back contacts of relay 158, 275, H, 175, back contacts of relay 263, 214, 265, back contacts of relay 153, 170, 169, 59, 25, contacts of relay 24 to battery B. The operation of relay 157 disconnects relay 155, there-by removing the operators telephone set from the tip and sleeve conductors. Relay 157 also closes the circuit of the guard lamp 244 by the same path as traced by the operation of relay 156. After the operator releases button 247, the circuit of relay 157 is controlled through the back contacts of relays 158 and 159. Relay 157 also connects the starting cam 231 to the stepping magnet 161 as follows: ground, cam contacts of 231, 189, contacts of relay 157, 201, 161, back contacts of relay 185 to battery B. As soon as the starting cam contacts are closed the wipers of the shifting switch at N O and P take one step and through portion N connect the impulse wire 191 to the tip side of the trunk 250, through the contacts of relay 160.

Whcn the No. 9 button in the row R is pressed, relay 160 will be held energized by the operation of cam 240,. until nine impulses have been transmitted by the commutator 242. These impulses operate the relay 29 (Fig. 2) as follows: ground 2 42, 191, 190, 192, contacts of relay 160, N, 250, F, 150, 167, 60, 54, 29, 42, cam springs 40 to battery B. Relay 29 responding to these impulses closes the circuit of the rotary magnet 34 of the switch D, thereby causing it to rotate and bring its wipers in line with a group of trunks in the ninth row.

At the first impulse sent over the tip conductor 150, the circuit of relay 180 is closed, and this relay operating, disconnects relay 179, and relay 179 falling back, disconnects relay 180 from. the tip conductor 150.

As soon as the cam springs associated with the rotary magnet 34 of the switch D are closed, ground is at once placed between the winding of the relay 29 and the coil 42, thereby shunting out the relay. Relay 29 falling back removes battery from the winding of the magnet 34 itself. It will be noted from this description that if the impulses were a trifle longer than necessary the relay 29 would be shunted out just as soon as the magnet 34 finishes its stroke.

After the rotary impulses have been transmitted the starting cam 231 causes the shifting switch to take another step, thereby connecting the impulse wire to the sleeve side of the trunk 251 through the portion N. Relay 160 is now held energized by the action of the cam 230 until a single test impulse is transmitted. This impulse operates relay 27, (Fig. 2) as follows: ground, 212, 191, 190,192, contacts of relay 160, N, 251, 151, 107, 61, lQ f'V 27, can. springs 10 to battery B.

Relay 27 after receiving this impulse is held energized as follows: battery B, con tacts of relay 25, contacts of relay 27, 58, contacts of relay 28, 72, 32, cam springs 41, to ground. These cam springs are closed when the switch D takes its first rotary motion. The operation of relay 27 closes the circuit of the vertical magnet 33 as follows: battery B, contacts of relay 28, 71, contacts of relay 27, 33 to ground. The magnet 33 in operating, closes the circuit of relay 28, which in turn opens the circuit of the magnet itself. The action of this relay and magnet causes the vertical stepping of the switch D. \Vhen the circuit of relay 28 is closed by the action of the magnet 33, the circuit of relay 27 is partially opened, but it will remain energized by the test wiper 57 in passing over grounded or busy contacts. When the relay 28 is operated and wiper 57 engages an idle contact, then relay 27 will at once becomedeenergized and disconnect the vertical magnet 33, thereby causing the switchD to bring its wipers to rest on contacts of an idle second selector. The controlling of the test relay 27 in the foregoing manner insures a full step of the magnet 33, as the wiper 57 fully engages its contact be fore the relay 27 is opened by the action of relay 28. i

As soon as the switch D takes its first vertical step, or, while in the act of doing so, cam springs 40 are opened, thereby disconnecting relays 27, and 29, respectively from the tip and sleeve sides of the trunk.

At the third rotation of the sending device, impulses corresponding to the hun dreds in the strip of buttons S are sent over the tip side of the trunk to the second selector E (Fig. 3,) operating the relay 81. This relay is connected to the tip side of the trunk 90 through the cam springs 88. The action of relay 81 closes the circuit of the rotary magnet 85, thereby causing the switch E to rotate and bring its wipers in line with contacts leading to connector switches. The operation ofrelay 81 also closes the circuit of relay 80. This latter relay when energized, remains locked to ground through the test wiper of the first selector switch D. The action of relay 80 disconnects, or opens the circuit of the release magnet 93.

At the fourth rotation of the sending device a single test impulse is sent over the sleeve side of the trunk, operating relay 83. This relay closes the circuit of the vertical magnet 84, causing the switch to step vertically until the test wiper 102 engages contacts leading to an idle connector switch. The test wiper 83 is controlled in the same manner as the test relay 27 (Fig. 2) and the rotary relay and rotary magnet are controlled, or regulated in the same manner as the rotary magnet 34, and rotary relay 29 in Fig. 2. At the first vertical step of the switch E the cam springs 88 are opened, thereby disconnecting relays 81 and 83, re spectively from the tip and sleeve sides of the trunk.

The calling subscriber is now connected to the contacts leading to an idle connector switch.

At the fifth rotation of the sending device, impulses corresponding to the button depressed in the row V (Fig. 9) are sent over the tip side of the trunk operating relay 310' of the connector (Fig. 4.) The action of this relay closes the circuit of the stepping magnet 360 of the party line distributing switch by. the following path: ground, 321,

contacts of relay 330, 323, 300, 318, contacts of relay 320 to battery B. The switch F takes a number of steps corresponding to the impulses determined by the depressed button in the row V (Fig. 9). In the present instance, I have shown the generator 356, connected to the first two contacts in the bank J, so that if either one or two impulses are transmitted, this generator will be connected to the sleeve side of the trunk 304. If six or seven impulses are transmitted, the same generator will be connected to the tip side of the trunk The contacts are arranged in this manner so one of the party line frequencies can also be used for straight or independent line ringing. We will assume that five impulses have been transmitted. Therefore generator 359 will become connected through the fifth contact of the bank J to the sleeve contact in the ringing relay 340. while ground is connected from the bank H to the tip contact of the ringing relay. 340.

The action of relay 310 also closes the circuit of relay 315, by the following path: battery B, 319, 315, contacts of relay 305, 306, 102, (Fig. 3), 89, contacts of relay S2 to ground.

At the sixth rotation of the sending device, impulses corresponding to the button depressed in the row T are sent over the sleeve side of the trunk, operating relay 305. This relay operating, unlocks relay 315, and closes the circuit of the rotary magnet 355 by the following path battery B, contacts of relay 305, 314, cam springs 380, 316, 355 to ground. This magnet operating, causes the connector switch G to rotate and cause its wipers to come opposite a group of contacts in which the desired line is located. The action of relay 305 also closes the circuit of relay 330. The action of this relay disconnects the stepping magnet 360 of the switch F and in its place connects the vertical magnet 350.

At the seventh rotation of the sending ea vice, units impulses corresponding to the f epressed button in the row T, are sent o er the tip side of the line operating relay 310 again. The relay responding, now operates the vertical magnet 350, causing the switch G to step vertically and bring the wipers into engagement with contacts leading to the desired line. The action of relay 310 again energizes relay 315, preventing annoying clicks while the wipers are passing over busy contacts.

When the switch G takes its first vertical step, the cam springs 380 operate and disconnect the rotary magnet 355.

At the eighth rotation of the sending device, a single test impulse is sent over the sleeve side of the trunk, operating relay 305 again. This relay now operating, connects the test relay 345 directly to test wiper 391. If the called line is busy, this relay 3 15 will become energized and lock itself from battery to one terminal and t0 ground,through the other terminal through the test wire 306. The action of this relay places ground on the release magnet 365, and causes the switch G to restore and also connects a busy tone from the wire 341 to the trunk 301, notifying the calling subscriber that the line is busy.

In case the called for line is not busy, the relay 3 15 will not be affected. Relay 305 acting again unlocks 315, and falling back places the relay 325 in series with the cut-off relay (Fig. 5) by the following path: battery B, contacts of relay 315, 312, 325, 311, contacts of relay 305, 308, 391, cut-off relay to ground. The action of thecut-off relay disconnects the line relay. The action of the relay 325 closes the sleeve side of the trunk,

as indicated by the heavy lines, and disconnects the repeating relay 310. Relay325 places battery to the winding of the tip relay 320, and also closes the circuit of the ringing relay 340 by the following path: ground, commutator 370, 340, 326, contacts of relay 325, 324, contacts of relays 330 and 315, 322, vertical magnet 350 to battery B. The action of this ringing relay connects the generator 359 to the sleeve conductor 304C and ground to the tip conductor 302,

thus ringing the subscribers bell AA at in tervals. At each actuation of the relay 340, a suitable tone test is sent over the sleeve side of the trunk through the condenser 570 and coil 665 notifying the calling subscriber that the called-for party is being rung.

At the next rotation of the sending device, relay 158 (Fig. 8) is connected to battery B through the portion P of the shifting switch. The action of this relay connects ground to the stepping magnet 161, and opens the circuit of the trunk wire 275, thereby releasing relay 157. The magnet 161 will vibrate and cause the shifting switch to rotate until the wipers reach their normal or resting position.

The disconnecting of relay 157 allows relay 265 (Fig. 7) and relay 25 (Fig. 2) to fall back. The falling back of relay 265 closes the circuit of relay 266 as follows: battery B, contacts of relay 264, 266, back contacts of relay 179, 210, contacts of relay 26."), 211, cam springs K to ground. The operation of relay 266 connects ground'dircctly to the release magnet 166, thereby restoring the switch M to its normal position. The operation of relay'266 also operates relays 263 and 162 in series as follows: ground, contacts of relay 266, 263, 162, to battery B. The operation of relay 162 severs the trunk conductors while the operation of relay 263 closes the circuit of the stepping magnet 261 of the switch MM as follows: ground, back contacts of relay 285, contacts of relay 263, 261, to battery B. The operation of the magnet 261 causes the switch to rotate, thereby restoring the cam springs to their normal position. When the cam springs assume their normal position, the circuit of relay 266 is broken, thereby releasing relays 263 and 162, causing the switch MM to cease rotating.

The falling back of relay 25 (Fig. 2) closes the talking conductors, allowing the calling subscriber to become connected through to the connector switch.

The restoring ol' the switch M releases the key-board and secondary trunk from the primary trunk, thereby preventing the interference by the operator, while the subscribers are conversing.

When the called subscriber removes his receiver during the non-ringing interval, the circuit of relay 320 is closed. The action of this relay unlocks relay 330 and disconnects relay 305. The falling back of relay 330 prevents further action of the ringing relay 3 1-0. The talking circuit of the calling and called subscriber is indicated throughout the various figures by the heavy lines.

When the called subscriber hangs up his receiver, relay 320 falls back, and the circuit of magnet 360 of the switch F is closed as follows: ground, interrupter 353, I, 398, contacts of relay 330, contacts of relay 315, 321, contacts of relay 330, 323, 360, 318, to battery B, through the contacts of relay 320. The magnet 360 will continue to vibrate due to the action of the interrupter 353 until the wiper of the portion I rests on the contact 336. Just before the wiper I reaches this contact, the wiper at H closes the circuit of the release magnet 365 as follows battery B, 365, 332, H, 327 to ground through the contacts of relay 315. The action of magnet 365 restores switch G to its normal position.

The calling subscriber hanging up his re ceiver opens the circuit of relay 23, (Fig. 2) thereby allowing the circuit of the release magnet 32 to be closed as follows: batter i cam springs 38, 73, contacts of relay er contacts of relay 28, T2, 32, 41 to ground. Magnet 32 operating, releases primary switch C and it in restoring, opens the cam springs 38, thereby removing the shunt from magnet 35, allowing it to become energized over the following path: battery B, 35, 73, contacts of relay 23, 58, contacts of relay 28, 72, 32, 75, cam springs 41 to ground. The operation of magnet 35 releases the first selector switch D. When this switch reaches its normal position, the cam springs 41 are opened, thereby breaking the circuit of the magnet 35.

When the test wiper of the first selector switch D leaves the test contact, leading to the second selector switch, the circuit of relay 80 (Fig. 3) is broken. This relay falling back closes the circuit of the release magnet 93, thereby causing the switch E to return to its normal position. \Vhilc the switch E is restoring ground is connected, directly to the test wire leading to the test contacts in the first selector switch banks, through the back contacts of relay 80. After the switch E reaches its normal position the cam springs 87 are opened, thereby removing ground, and placing the switch E in condition to be selected by other first selector switches.

In case the called-for party does not answer, then the calling subscriber also controls the release of the connector switchin the following manner: When the second selector switch (Fig. 3) restores, ground is removed from the test wire 306, thereby unlocking relay330 just as though the called subscriber had answered. Relay 330 falling back and relay 320 also being in its normal position, allows the circuit of the stepping magnet 360 to be closed by the path previously traced.

Having thus described my invention what I claimv and desire to secure by Letters Patent is:

1. A telephone exchange system, including an electrical circuit, selective switches, multiple terminals pertaining to said circuit at said switches normally unsclectable in character, a magnet individual to said circuit, means for operating said magnet, apparatus including a step by step switch responsive to said magnet to render said terminals selectable and to start a switch to select said circuit.

2. A telephone exchange system, including a telephone line, a line relay connected therewith, selective switches adapted to select said lines, multiple terminals associated with said line at said switches, apparatus including a step by step switch interposed beu 7 To, cam spruigs tween said line and said switches, said apparatus responsive to the operation of said line relay to render said terminals selectable by said switches.

3. A telephone exchange system. including a calling subscribers line, terminals therefor at the exchange, a primary link-circuit adapted to be automatically connected with said line on initiation of a call, an operators key-board, a link-circuit interposed between said primary link-circuit and keyboard comprising a secondary and tertiary switch, means controlled by the calling subscribers line to cause the primary link-circuit to automatically pick out the line, to cause the secondary switch to pick out primary link-circuit and the tertiary switch to pick out said key-board, operators means for transmitting directing current from said key-board to establish a connection from the terminals of the calling line to terminals of the called line with means thereon for freeing said secondary and tertiary switches.

4. In a telephone exchange system, a number of subscribers lines, a number of trunks less than the number of lines, each trunk terminating at one end in a primary selector switch, and at the other end in a first selector switch, an operators circuit and apparatus including a telephone set and :1 sending device, a secondary and tertiary switch interposed between said trunks and sending device, the secondary switch containing terminals leading to said trunks, the tertiary switch containing terminals leadin to said sending device, the primary, secondary and tertiary switches being responsive to the calling line so as to to connect the primary switch with a line, the secondary switch with a trunk, and the tertiary switch with a sending device.

5. In a telephone exchange system, a number of subscribers lines, a number of trunks less than the number of lines, each trunk terminating at one end in a primary selector switch and at the other end in a first selector switch, an operators position, a secondary and tertiary switch, means controlled by a calling subscribers line to cause the primary selector switch to automatically select the calling line, the secondary switch to automatically select said primary trunk and said tertiary switch to select said operators position.

6. A telephone exchange system, including a calling subscribers line, terminals therefor at the exchange, a number of trunks less than the number of lines, each trunk terminatin at one end in a primary selector switch and at the other end in a first selector switch, an operators position, a secondary and an associated tertiary switch, means controlled upon the initiation of a call to cause the primary selector switch to automatically 

